Treatment of hydrocarbons



Patented June 20, 1944 2,351,624 TREATMENT OF HYDROCARBONS Julian M.Mavity, Chicago, 111., assignor to Universal Oil Products Company,Chicago, 111., a

corporation of Delaware No Drawing. Application October 31, 1940 SerialNo. 363,684

3 Claims.

This invention relates to the treatment of hydrocarbons of substantiallymotor fuel boiling range having low antiknock value such as straight-rungasolines and naphthas from parafllnic and naphthenic crude oils orthermally cracked gasolines to improve their antilmock characteristics.The process is also applicable to low boiling hydrocarbons produced fromhydrocarbon materials generally including synthetic oils derived fromlignites, coals and shales.

More specifically, the invention has reference to a catalytic reformingprocess which utilizes operating conditions under which no substantialamount of strictly pyrolytic reactions occur. The catalysts areparticularly effective in dehydrogenation and also cyclizationreactions, and are of importance because of their refractory naturewhich enables them to retain their catalytic properties for prolongedperiods" oftime under commercial conditions of use and regeneration.

tion of the double bonds, the degree of saturation of the straight chainand cyclic hydrocarbons, and the presence of other substances in minoramounts which influence the rate of combustion of the fuel. Although theantiknock value may be increased in part as a result of the loss ofhydrogen, various other reactions may also occur such as isomerizationinvolving the formation of branched chain hydrocarbons either saturatedor unsaturated and the shifting of double bonds, or cyclization andaromatization involving the formation of hydrocarbons of a cycliccharacter with or without paraflinic and unsaturated side chains.

In one specific embodiment the invention comprises the reformingtreatment of hydrocarbon oils boiling substantially within the motorfuel boiling range and having low antiknook value whereby saidhydrocarbons are vaporized and subjected to contact with a catalystcomprising essentially an intimate mixture of specially prepared titaniasupporting an oxide of chromium,

whereby a motor fuel of high antiknock value is obtained.

According to the-present invention, hydrocarbon fractions boilingsubstantially within the as the result of various hydrocarbon conversionreactions such as cyclization, isomerization, dehydrogenation, hydrogentransfer, desulfurization, and to a minor extent carbon-to-carboncleavage reactions. In general, paraflinic and naphthenic hydrocarbonsare dehydrogenated to produce olefinic and aromatic hydrocarbons andmore or less isomerization takes place with the shifting of double bondsand the branching of less branched chain hydrocarbons.

The catalysts used are supported on a titanium oxide carrier. It isnecessary that the carrier for a suitable catalyst be of a refractorymaterial which will not sinter or fuse under the high temperatureconditions of useand regeneration when in prolonged service in thereforming of the hydrocarbon oils. It is also necessary that the carrierbe adaptable to the activating oxides so as to mutually provide thecatalytic surfaces promoting the above mentioned desired reactions. Thetitanium oxide used as a carrier is preferably in a relatively purestate and may be obtained from rutile, ilmenite, or othertitaniumcontaining material. The manufacture thereof is generally known,particularly in connection with the manufacture of paints where titaniumoxide has one of its main uses. Titanium oxide prepared as a paintmaterial is one form of titanium oxide preferably used as a. carrier forthe activating oxides suitable for the reforming of hydrocarbons. It isalso advantageous to use the titanium oxide in afine particle size,particles of 1 6 to 1 micron for example having been used with goodresults.

The oxides of chromium include the trioxide (1103, the dioxide CrOi andthe sesquioxide CrzOa. The last named is readily produced by treatingthe triosice under reducing conditions as in hydrogen containing gas, orin hydrocarbon vapors at temperatures above 250 C. The CraOa alsoresults from calcining CrOa to varying degrees depending on temperature,time and presence of other materials. The dioxide has been considered tobe an equimolecular mixture of the trioxide-and the sequioxide. Theseoxides may be developed readily on the surfaces and in the pores of thecarrier granules by impregnating with solutions of chromic anhydride ornitrate to produce primarily the trioxide which is then reduced to thesesquioxide to furnish the active catalyst for use in the presentprocess.

The catalytic oxide preferably used and the carriers vary. If too largean amount of the impregnating. components is used, the density of thecatalyst is increased and the porosity is decreased with a subsequentreduction of catalytically available surface. In the case of chromiumsesquioxide CrzOs, which is one of the preferred activating oxides forthe reforming reactions when properly supported, various proportions maybe used with good results such as from 2 to 30 weight per cent ofchromia with respect to titania. Lower and higher percentages of thechromia may give lower catalytic activity.

In the impregnating step, chromium trioxide may be dissolved in water toform a solution used to deposit the desired amount of chromic oxide onthe surface and in the pores of the titanium oxide particles aftersuitable heating. Subsequently, either in use or before using, thechromium trioxide is reduced to the active sesquioxide at temperaturesof approximately 500-700 C. In addition to the catalytically activecomponents impregnated into the catalyst a small proportion ofstabilizing agent may also be impregnated into the catalyst particles.It has been found that in the prolonged use of this type of catalyst,there is a gradual dropping ofi of activity due to a change in form ofthe active material. It has also been found that this tendency can becounteracted by adding small amounts of compounds leading to theformation of metal oxides, more particularly oxides such as those ofmagnesium and zinc which form spinels. It is believed that double oxidesof this type may be formed with the catalyst components at the hightemperatures employed in the process which substantially prevent thechange of the chromium sesquioxide catalyst to a more inactive, form.

The titanium oxide carrier may be impregnated with the activating oxidesbefore it is formed into granules or it may be impregnated after forminginto particles. Thus the titanium oxide may be mixed with a lubricantand formed into pellets ina pilling machine, and subsequently heated inair at a temperature of approximately 500 C. to decompose and remove thelubricant. The pelleted material is then impregnated with solutions ofthe metal compounds which are to be decomposed to produce the activatingmetal oxides. The titanium oxide carrier may also be shaped intoparticles by other methods such as extrusion or pressing with subsequentgranulation and the particles thus formed impregnated similarly asabove. The activating oxides or compounds from which they are producedmay also be incorporated into the carrier before it is shaped intoparticles in which case the heating and calcination after shaping intoparticles removes any lubricant which may be employed and may alsoconvert the impregnated material into the desired active form forreaction.

The catalyst particles are suitable employed in beds and thehydrocarbons to be treated are vaporized and contacted with the catalystbeds at regulated temperature, pressure and time conditions. Thetemperature of the catalyst bed is so regulated as to compensate .forthe endothermic and exothermic conditions occurring during the reactionand reactivation periods. While in use there is a deposition ofcarbonaceous material upon the catalytic surfaces as a result ofsecondary reactions. This gradually reduces the catalytic reaction andwhen the reaction has dropped off materially, the catalyst isregenerated by the oxidation of the carbonaceous materials using anoxygen-containing gas. The temperature is regulated during the burningof these deposits as before indicated so as to avoid heating thecatalyst to unnecessarily high temperatures which may gradually reduceits activity. Various means such as regulating the oxygen concentrationin the gases and the volume of said gases or removing heat byheat-absorbing means are the more common methods employed.

The hydrocarbon oil fraction which is to be processed is vaporized andsubjected to contact with the above catalyst at a temperature of theorder of 450-700 C. and under a pressure from substantially atmosphericto approximately 500 pounds or more per square inch. The rate at whichthe hydrocarbon vapors are passed over the catalyst may vary fromapproximately 0.1 to 40 volumes of liquid charge per hour per volume ofcatalyst space in the reactor.

The titanium oxide supported catalyst is not restricted to use asparticles in a granular mass since the catalyst can be used as a finelydivided powder and contacted with the vapor or disposed in a stream ofthe hydrocarbon oil to be reformed, and processedunder suitableconditions of temperature, pressure and contact time to produce largeyields of the desired high antiknock gasoline. The powdered catalyst maythen be separated from the high antiknock gasoline and from the adheringoil by various procedures and the separated catalyst is then regeneratedby removing hydrocarbonaceous deposits by solvent treatment and/orheating in the presence of air or oxygen-containing gases in order to'remove the deposited material. The

regenerated catalyst is then used either alone or in mixture with freshcatalyst suspended in the hydrocarbon oil or vapors processed.

The following specific example is given to illustrate the process, amethod of catalyst preparation also being given. The process should notbe considered as limited to the example nor to the particular catalystpreparation since these are given merely as illustrations of the noveltyand utility of the invention.

The titanium dioxide carrier for the catalyst of the following exampleis a very finely divided titanium dioxide of approximately 99% purityand having an average particle size between 1 and 1 microns. The drycarrier is mixed with a small amount of a hydrogenated vegetable oillubricant to facilitate pelleting and is formed into A; by A; inchcylindrical pellets. The peling the approximate composition of 8% CraOaand 92% TiOz. The impregnated pills are then dried and calcined at atemperature of approximately 500 C.

A Mid-Continent straight-run naphtha having an end-point ofapproximately 205 C. and an octane number of 41 was vaporized andpreheated to a temperature of approximately 575 C. and contacted withthe above described chromium sesquioxide-titania catalyst disposed in areactor at substantially atmospheric pressure using a liquid spacevelocity of approximately 1.49. Smaller and higher space velocities maybe employed without materially affecting the character of the product.The treated vapors were then condensed and 205 C. end-point gasoastmaaline and gas separated from the products. The recovered motor 'fuelcorresponded to 87 volume per cent of the naphtha charged to the processand had an octane number of 67 by the motor method.

I claim as my invention:

1. A process for treating hydrocarbons of approximately motor iuelboiling range to increase the antiknock value thereof which comprisessubjecting said hydrocarbons at a temperature from about 450 to about700 C. and at a pressure from about atmospheric to about 500 pounds persquare inch to contact with a catalytic material comprising essentiallya major proportion of titanium oxide supporting a minor proportion ofchromium oxide.

2. A process for increasing the antiknock value of hydrocarbons boilingin the gasoline range which comprises subjecting the hydrocarbons toreforming conditions in the presence of a chromium oxide dehydrogenatingcatalyst supported on a relatively pure titanium oxide of an averageparticle size of about 5 to 1 microns. 3. A process for increasing theantiknoclt value of hydrocarbons boiling in the gasoline range whichcomprises subjecting the hydrocarbons to reforming conditions in thepresence of a catalyst comprising a major proportion of titanium oxidesupporting a minor proportion of chromium oxide.

JULIAN M. MAVI'IY.

